中朝古地块元古宙构造、地层的某些问题

<正> 近年来,在前寒武纪中朝古地块上已测得几组超过30亿年,接近35亿年的放射性年龄(3330Ma/U-Pb,3257Ma/Rb-Sr,3500/Sm-Nd,3479Ma/Rb-Sr,3670Ma/Rb-Sr)及相当丰富的大于25亿年的U-Pb、Pb-Pb、Rb-Sr年龄(王东方等1984),进一步说明该地块是一个最初由云英、长英片麻岩、绿岩/花岗岩组成的太古宙古陆核。在此基础上,经元古宙

Some problems concerning Proterozoic structure and strata of the Sino-Korean Old Land

Based on abundant radiometric dating, palaeontological and stratigraphical data, the stra-tigraphical positions of the Xihe (900-800ma), Liaonan (800-600 ma) and Liaohe (2300-1700 ma) Groups in eastern Liaoning have been determined. Mistakes that the Changcheng Group is younger than the Liaohe Group and the Xihe Group is considered to be equivalent to the Changcheng Group have been pointed out. The netlike spaces among Archean nuclei of continent were filled with sedimentary accu mulations in the early stage of Proterozoic eon after those nuclei were formed. Since then, there have been two kinds of structural areas: compressed geocyclinal area with highly deformed and metamorphozed rocks and stretch rift filled with sediments unmetamorphozed and undeformed essentially, such as Yanshan, Jiaoliao, Yuxi-Taihangshan and north margin rift belts on Sino-Korean Old Land. These rift belts developed inheritably into a huge fault belt during Phanerozoic eon. The two kinds of structural belts on earlier Proterozoic earth crust developed separately and conjugately. This is the reason why no direct contact relationship between metamorphozed Liaohe and Hutuo Groups and Changcheng Group has yet been known.In the Early Proterozoic, stretch structures are mostly important, so, at present, a lot of contradictions in stratigraphic correlation have resulted from using simply the principle of Phanerozoic stratigraphic relationship, which was formed in wide trarsgression and regression on certain-scale platform. Therefore, study of Jixian-type section of Proterozoic supergroups on Sino-Korean Old Land needs to research the rift-type structure in which they are present.